For planar semiconductor devices such as metal oxide field effect transistors (MOSFETs), heat generated from a passage of an electric current through semiconductor material is passed down to a substrate and dissipated. Therefore, a temperature detector, such as a diode or a bipolar junction transistor (BJT), is usually configured to detect a temperature of a chip, or a large area including many transistors. Such temperature detector is typically as large as 5−5 μm2.
As process node advances, non-planar semiconductor devices such as fin field effect transistors (FinFETs) and nanowire field effect transistors (nanowire FETs) are being considered to replace the planar semiconductor devices to mitigate short channel effects, increase on-state currents, etc. Because of confined geometry of a non-planar device, heat generated when the device is operating is more difficult to be passed down to a substrate and dissipated, and therefore increases temperature at a particular location of the device, resulting in “local” self-heat. Local self-heat accelerates aging and reduces lifespan of the device. An increase of 10° C. to 15° C. in the device can result in about 2 times reduction in the lifespan of the device. Local self-heat also has a major impact on electromigration reliability of metal interconnects associated with the device that are thermally coupled to the heated location in the device. The mean time to failure of the circuit due to electromigration decreases as temperature of the metal interconnects increase.
Temperature detectors for planar devices are too large to detect a local temperature of a non-planar device.
Like reference symbols in the various drawings indicate like elements.